This invention relates generally to telephone line monitoring and alarm apparatus, and more specifically to an apparatus for continuously monitoring the status of a telephone line and activating an audio-visual alarm if the telephone line becomes inoperative due to intentional or accidental disruption of telephone service.
Telephone service to a subscriber may be disrupted as a result of a malfunction occurring on the utility-provided central office line or on-premise subscriber line. A telephone line may become inoperative due to accidental breakage or shorting, as may occur from inclement weather, or through deliberate action, such as during a burglary in which the on-premise subscriber line is cut to disconnect an alarm system from a central monitoring station or prevent a victim from calling for assistance. Regardless of the cause of the disruption, the telephone subscriber will be without telephone service and will, in general, not be aware that the telephone line is inoperative. It is therefore desirable to have a simple and reliable telephone line monitor and alarm means which functions to continuously monitor the integrity of the telephone line and alert a subscriber by both visual and auditory signals if a disruption in telephone service occurs.
Apparatus designed to assess the status and integrity of a telephone line may be broadly grouped into two principal types: 1. Intermittent use test instruments intended primarily for use by professionals skilled in telephone system maintenance and repair. Equipment of this kind typically includes a variety of display devices such as meters or LED indicators and may be specifically adapted to test for line faults by interconnection to the central office or subscriber segment of the telephone line 2. Continuous line monitoring apparatus intended as on-premise devices which are connected directly to the subscriber segment of the telephone line and provide continuous fault detection and alarm warning if service is disrupted. Both types of apparatus may test for open circuit, line-to-ground faults, the presence of extraneous AC voltage, or abnormal impedance characteristics in either the tip or ring conductors of the telephone line. Moreover, telephone line test and monitoring devices may be based on simple line voltage sensing, impedance measurement by means of current sensing, or extraneous AC voltage fault detection.
In the case of telephone line monitoring apparatus intended for continuous use on the subscriber premises, the primary objective is to alert the subscriber by both visual and auditory means if telephone service is disrupted. Advances in the current art of continuous telephone line monitoring apparatus are needed in order to meet this objective in a reliable, cost-effective and simple manner based on innovative features which also enhance product convenience and manner of use.
It is appreciated that numerous telephone line monitors are known in the art. Examples are U.S. Pat. No. 5,696,810 to Dunn, U.S. Pat. Nos. 5,056,131 and 4,969,179 to Kanare and Rehler, and U.S. Pat. No. 4,969,178 to Chen and Loao.
In U.S. Pat. No. 5,696,810, an apparatus is disclosed for monitoring the integrity of a telephone line and for warning when the line is inoperative. The device comprises a monitoring unit which continuously senses line voltage and generates a control signal which assumes a first value when the line is operational and a second value when the line is inoperative. A battery powered audio alarm is activated when said control signal assumes a second value corresponding to an inoperative line condition. Connection of the device to the telephone line is made by means of a standard telephone cable and plug.
Exemplary continuous telephone line monitors which provide both visual and auditory alarms if the telephone line becomes inoperative may be found in U.S. Pat. Nos. 5,056,131 and 4,969,179. In U.S. Pat. No. 5,056,131, there is provided means for activating a self-flashing light emitting diode and an auditory sounder having alternating loud and soft output in response to a detected low voltage fault condition on the telephone line. The monitoring and alarm circuitry is powered by a battery, or by an AC source with battery back-up. U.S. Pat No. 4,969,179 discloses a continuous telephone line monitor which activates a light emitting diode and auditory sounder if line voltage falls below approximately 6 VDC, corresponding to a short or open circuit fault condition. In both disclosures connection of the device to the telephone line is made in standard fashion by means of a telephone cable and plug.
In U.S. Pat. No. 4,969,178 a multipurpose subscriber telephone line monitor is provided which uses a voltage detecting circuit, a current detecting circuit, two control circuits and a comparator circuit to detect open-circuit, short-circuit, or illegal connection of the subscriber local line. An alarm circuit is employed to generate an audio alarm signal when the telephone line becomes inoperative.
In summary, the prior art has evolved to provide varied and effective means for continuous telephone line monitoring and alarm activation in response to fault conditions having accidental or deliberate origin and which result in a disruption in telephone service to a subscriber. However, simple and reliable means for connecting a telephone line monitor to a standard telephone line, have either not been addressed, or have involved the use of hard-wiring or cable-plug attachments to effect said monitor-telephone line connection. The use of hard-wired connections or cable-plug attachments may be undesirable in many routine consumer applications, however, because of the need for special skills in the case of hard-wiring and the loss of telephone jack access for other telecommunication equipment in the case of cable-plug configurations. Moreover, although the prior art is predominantly based on battery powered or battery back-up operation to activate alarms in the event of telephone service disruption, little or no attention has been given to low battery voltage sensing and audio-visual warning to permit battery replacement in a timely manner in order to ensure on-going product reliability. Finally, the prior art in continuous telephone line monitors has not provided for a simple and effective means to indicate that the device is ON and operational as opposed to connected but in the OFF state, a feature which is of significant importance in view of the intended application.
Therefore, in many continuous telephone line monitoring applications, it is desirable to provide a simple and reliable means for continuously monitoring telephone line status and activating an audio-visual alarm if the telephone line becomes inoperative, comprising direct plug-in connection to a standard telephone wall jack as a self-contained and autonomous unit without interconnecting cables or cable-plug attachments. It is further desirable for said apparatus to provide integral means to permit the uninterrupted use of standard telecommunication equipment, such as telephones, answering machines, or facsimile equipment, with said monitoring and alarm apparatus. Moreover, telephone monitoring and alarm apparatus must incorporate audio-visual low battery indicating means and ON status indicating means to be effective in continuous-use consumer applications.
It is thus an object of the present invention to provide a telephone line monitor and alarm means capable of continuously monitoring line status and activating an audio-visual alarm if the telephone line becomes inoperative, said means capable of direct plug-in connection to a standard telephone wall jack as a self-contained and autonomous unit without interconnecting cables or cable-plug attachments.
It is a further object of the present invention to provide a dual jack splitter as an integral part of said self-contained and autonomous telephone line monitor and alarm means, in order to permit the uninterrupted use of standard telecommunication equipment, such as telephones, answering machines, or facsimile equipment, with said monitor and alarm means plugged into a standard telephone wall jack.
It is a further object of the present invention to provide continuous battery voltage sensing and audio-visual low battery voltage indicating means in order to alert the user of the need to replace the battery in said self-contained and autonomous telephone line monitor and alarm means.
It is a further object of the present invention to provide a simple visual means of ON status indication in said self-contained and autonomous telephone line monitor and alarm means.
It is a further object of the present invention to provide the mechanical configurations for said self-contained and autonomous telephone line monitor and alarm means, so as to permit the implementation of said means in a simple and reliable manner, thereby improving performance while at the same time maintaining a high level of reliability in continuous telephone line monitoring and alarm apparatus.
To achieve the foregoing objects, and in accordance with the purposes of the invention as embodied and broadly described herein, there is provided an apparatus comprising a mechanical enclosure and associated electrical circuit, a telephone plug and dual jack splitter communicating with said electrical circuit means and forming permanent and integral parts of said mechanical enclosure means.
According to an advantageous embodiment of the mechanical enclosure according to the invention, a telephone plug having electrical contacts and mechanical design compatible for use with standard telephone jacks, is moulded as an integral part of said mechanical enclosure means, or comprises a separate component and permanently attached to said means.
According to another advantageous embodiment of the mechanical enclosure according to the invention, a dual telephone jack splitter having electrical contacts and mechanical design compatible for use with standard telephone plugs found on telecommunication equipment, is moulded as an integral part of said mechanical enclosure means, or comprises a separate component and permanently attached to said means.
According to yet another advantageous embodiment of the mechanical enclosure according to the invention, said telephone plug is situated on the back face of said mechanical enclosure means and said dual jack splitter is situated on the front face of said mechanical enclosure means.
To implement the foregoing advantageous features in accordance with the invention as embodied and broadly described herein, there is provided a circuit for continuous telephone line monitoring means, audio-visual alarm means, audio-visual low battery voltage indicating means and ON status indicating means.
According to an advantageous embodiment of the circuit according to the invention, telephone line voltage is continuously monitored by a battery operated micropower voltage threshold responsive circuit, for example by an IC comparator or discrete FET-input configuration, wherein said voltage threshold responsive circuit assumes a first xe2x80x9cnormalxe2x80x9d output state when telephone line voltage is above a predefined threshold value corresponding to standard telephone line operation, and a second xe2x80x9calarmxe2x80x9d output state if telephone line voltage falls below standard telephone line voltage requirements, corresponding to loss of telephone service.
According to an advantageous feature of this embodiment, said telephone line voltage threshold responsive circuit means is capable of activating an audio alarm oscillator and visual alarm driver circuit upon assuming said second xe2x80x9calarmxe2x80x9d output state, the audio oscillator means driving an audio alarm component, for example a piezo acoustic element, and the visual alarm driver circuit activating a visual alarm component, for example a light emitting diode (LED), said audio-visual alarm being distinctively associated with loss of telephone service.
According to another advantageous embodiment of the circuit according to the invention, battery voltage is continuously monitored by a micropower voltage threshold responsive circuit, for example by an IC comparator or discrete FET-input configuration, wherein said voltage threshold responsive circuit assumes a first xe2x80x9cnormalxe2x80x9d output state when battery voltage is greater than a predefined threshold value, corresponding to an acceptable battery state of charge, and a second xe2x80x9calarmxe2x80x9d output state if battery voltage falls below said predefined threshold, indicating that battery replacement is necessary.
According to an advantageous feature of this embodiment, said battery voltage threshold responsive circuit means is capable of activating an audio alarm oscillator and visual alarm driver circuit upon assuming said second xe2x80x9calarmxe2x80x9d output state, the audio oscillator means driving an audio alarm component, for example a piezo acoustic element, and the visual alarm driver circuit activating a visual alarm component, for example an LED, said audio-visual alarm being distinctively associated with low battery voltage.
According to yet another advantageous embodiment of the circuit according to the invention, ON status indication is provided by a micropower pulse generating circuit based on IC or discrete component timer configurations, said pulse generating circuit activating a visual indicating component, for example an LED.